Freestanding metallic nanowires attached to a metallic substrate are disclosed. A method of creating the nanowire structure using an anodized layer is presented. One embodiment of the present invention relates to Surface-Enhanced Raman Scattering (SERS) based sensor heads or devices and systems incorporating such devices, and methods for molecular identification based on SERS. Analytic techniques for detecting, discriminating, and quantifying various molecular species in blood, air, water, and soil samples or analytes are generally known. These include fluorescence microscopy, chromatography, photometry and spectroscopy. Spectroscopy is a commonly used analytical technique for screening chemical and biological samples in laboratories and hospitals. It involves the measurement of the interaction of radiant energy with matter and the interpretation of the interaction. Interpretation of the spectra produced by various spectroscopic instruments has been used to provide fundamental information on atomic and molecular energy levels, the distribution of species within those levels, the nature of processes involving change from one level to another, molecular geometries, chemical bonding, and interaction of molecules in solution. Comparisons of spectra have provided a basis for determining qualitative chemical composition and chemical structure, and for quantitative chemical analysis.
Raman spectroscopy (relying upon Raman effect) provides definitive information about the molecular structure of a material by investigating its vibrational spectrum. Different molecular species exhibit different Raman spectra. In fact, isomers of the same molecular species can be distinguished by this technique.
Surface Enhanced Raman Scattering (SERS) techniques may employ small structured materials. Noble metal nanoparticles exhibit very strong optical absorption in the ultra-violet through the visible range of the spectrum, which is not observed in their bulk counterparts. The absorption leads to tremendous electric field enhancement at the particle surface and in the regions between neighboring nanostructures. This field enhancement affect is utilized in SERS, by employing nanostructured materials to boost the Raman signal intensity. SERS techniques have often led to increases in the effective Raman cross-section by factors of 1014-1015, allowing the Raman spectra of single molecules to be probed in relatively short times (e.g., tens of seconds).